The best types of wood to use are hard, slow-burning ones that release a lot of heat such as oak, beech, ash, birch and olive. Don’t use pine logs, as they will spit aggressively and the resin will release lots of black smoke on burning. This resinous smoke will also give an unpleasant flavour to the food. Pine smoke will also produce a lot of soot that, over time, will clog up your oven’s chimney. Avoid using broken up wooden pallets, and other treated wood such as fence posts, because they will release chemical toxins on burning.